Method and apparatus for transmitting and receiving wireless signal in wireless communication system

ABSTRACT

The present invention relates to a wireless communication system, more specifically, to a method and an apparatus therefor, the method comprising the steps of: merging a first cell having a first TTI and a second cell having a second TTI, the length of the second TTI being N (N&gt;1) times the length of the first TTI; receiving data scheduling information for the second cell in the first TTI of the first cell; and establishing data communication on the basis of the data scheduling information in the second TTI of the second cell corresponding to the first TTI of the first cell, wherein the first TTI for the first cell is any one TTI from among the N number of TTIs of the first cell corresponding to the second TTI of the second cell.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for transmitting/receivinga wireless signal. The wireless communication system includes a CA-based(Carrier Aggregation-based) wireless communication system.

BACKGROUND ART

Generally, a wireless communication system is developing to diverselycover a wide range to provide such a communication service as an audiocommunication service, a data communication service and the like. Thewireless communication is a sort of a multiple access system capable ofsupporting communications with multiple users by sharing availablesystem resources (e.g., bandwidth, transmit power, etc.). For example,the multiple access system may include one of CDMA (code divisionmultiple access) system, FDMA (frequency division multiple access)system, TDMA (time division multiple access) system, OFDMA (orthogonalfrequency division multiple access) system, SC-FDMA (single carrierfrequency division multiple access) system and the like.

DISCLOSURE OF THE INVENTION Technical Task

An object of the present invention is to provide a method of efficientlytransmitting/receiving control information in a wireless communicationand an apparatus therefor.

Technical tasks obtainable from the present invention are non-limitedthe abovementioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, accordingto one embodiment, a method of performing communication by a userequipment in a wireless communication, includes: aggregating a firstcell having a first TTI (Transmission Timer Interval) length with asecond cell having a second TTI length, wherein the second TTI lengthcorresponds to N (N>1) multiple of the first TTI length, receiving datascheduling information for the second cell within a first TTI of thefirst cell, and performing data communication within a second TTI of thesecond cell corresponding to the first TTI of the first cell based onthe data scheduling information. In this case, the first TTI of thefirst cell may correspond to one of the N TTIs of the first cellcorresponding to the second TTI of the second cell.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a different embodiment, auser equipment in a wireless communication system includes: an RF (RadioFrequency) module and a processor, the processor configured to aggregatea first cell having a first TTI (Transmission Timer Interval) lengthwith a second cell having a second TTI length, wherein the second TTIlength corresponds to N (N>1) multiple of the first TTI length, theprocessor configured to receive data scheduling information for thesecond cell within a first TTI of the first cell, the processorconfigured to perform data communication within a second TTI of thesecond cell corresponding to the first TTI of the first cell based onthe data scheduling information. In this case, the first TTI of thefirst cell may correspond to one of the N TTIs of the first cellcorresponding to the second TTI of the second cell.

Preferably, the N TTIs of the first cell corresponding to the second TTIof the second cell are divided into TTI groups and the first TTI of thefirst cell corresponds to a TTI belonging to a specific TTI group amongthe TTI groups.

Preferably, a position of a TTI corresponding to the first TTI of thefirst cell may vary over time in the specific TTI group.

Preferably, the first TTI of the first cell may correspond to a TTIoverlapped with a first OFDM symbol in time domain among a plurality ofOFDM (Orthogonal Frequency Division Multiplexing) symbols constructingthe second TTI of the second cell among the N TTIs of the first cellcorresponding to the second TTI of the second cell.

Preferably, the method can further include the step of sequentiallymonitoring the N TTIs of the first cell corresponding to the second TTIof the second cell to receive the data scheduling information for thesecond cell. In this case, if the data scheduling information for thesecond cell is detected, although there is a TTI to be monitored,monitoring on the N TTIs of the first cell can be terminated.

Preferably, a subcarrier spacing configured to the first cell may begreater than a subcarrier spacing configured to the second cell.

Advantageous Effects

According to the present invention, wireless signal transmission andreception can be efficiently performed in a wireless communicationsystem.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 illustrates physical channels used in 3GPP LTE(-A) and a signaltransmission method using the same.

FIG. 2 illustrates a radio frame structure.

FIG. 3 illustrates a resource grid of a downlink slot.

FIG. 4 illustrates a downlink subframe structure.

FIG. 5 illustrates an example of an Enhanced Physical Downlink ControlChannel (EPDCCH).

FIG. 6 illustrates the structure of an uplink subframe used in LTE(-A).

FIG. 7 illustrates Single Carrier Frequency Division Multiple Access(SC-FDMA) scheme and Orthogonal Frequency Division Multiple Access(OFDMA) scheme.

FIG. 8 illustrates UL HARQ (Uplink Hybrid Automatic Repeat reQuest)operation.

FIG. 9 and FIG. 10 illustrate examples of a random access procedure.

FIG. 11 illustrates uplink-downlink frame timing relation.

FIG. 12 illustrates a carrier aggregation (CA)-based wirelesscommunication system.

FIG. 13 illustrates cross-carrier scheduling.

FIG. 14 illustrates analog beamforming.

FIG. 15 illustrates a structure of a self-contained subframe.

FIGS. 16 to 19 illustrate signal transmission according to the presentinvention.

FIG. 20 illustrates a base station and a user equipment applicable to anembodiment of the present invention.

BEST MODE Mode for Invention

Embodiments of the present invention are applicable to a variety ofwireless access technologies such as code division multiple access(CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), orthogonal frequency division multiple access(OFDMA), and single carrier frequency division multiple access(SC-FDMA). CDMA can be implemented as a radio technology such asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented as a radio technology such as Global System for Mobilecommunications (GSM)/General Packet Radio Service (GPRS)/Enhanced DataRates for GSM Evolution (EDGE). OFDMA can be implemented as a radiotechnology such as Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wireless Fidelity (Wi-Fi)), IEEE 802.16 (Worldwideinteroperability for Microwave Access (WiMAX)), IEEE 802.20, and EvolvedUTRA (E-UTRA). UTRA is a part of Universal Mobile TelecommunicationsSystem (UMTS). 3rd Generation Partnership Project (3GPP) Long TermEvolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA,employing OFDMA for downlink and SC-FDMA for uplink. LTE-Advanced(LTE-A) evolves from 3GPP LTE. While the following description is given,centering on 3GPP LTE/LTE-A for clarity, this is purely exemplary andthus should not be construed as limiting the present invention.

In a wireless communication system, a user equipment (UE) receivesinformation through downlink (DL) from a base station (BS) and transmitinformation to the BS through uplink (UL). The information transmittedand received by the BS and the UE includes data and various controlinformation and includes various physical channels according totype/usage of the information transmitted and received by the UE and theBS.

FIG. 1 illustrates physical channels used in 3GPP LTE(-A) and a signaltransmission method using the same.

When powered on or when a UE initially enters a cell, the UE performsinitial cell search involving synchronization with a BS in step S101.For initial cell search, the UE synchronizes with the BS and acquireinformation such as a cell Identifier (ID) by receiving a primarysynchronization channel (P-SCH) and a secondary synchronization channel(S-SCH) from the BS. Then the UE may receive broadcast information fromthe cell on a physical broadcast channel (PBCH). In the meantime, the UEmay check a downlink channel status by receiving a downlink referencesignal (DL RS) during initial cell search.

After initial cell search, the UE may acquire more specific systeminformation by receiving a physical downlink control channel (PDCCH) andreceiving a physical downlink shared channel (PDSCH) based oninformation of the PDCCH in step S102.

The UE may perform a random access procedure to access the BS in stepsS103 to S106. For random access, the UE may transmit a preamble to theBS on a physical random access channel (PRACH) (S103) and receive aresponse message for preamble on a PDCCH and a PDSCH corresponding tothe PDCCH (S104). In the case of contention-based random access, the UEmay perform a contention resolution procedure by further transmittingthe PRACH (S105) and receiving a PDCCH and a PDSCH corresponding to thePDCCH (S106).

After the foregoing procedure, the UE may receive a PDCCH/PDSCH (S107)and transmit a physical uplink shared channel (PUSCH)/physical uplinkcontrol channel (PUCCH) (S108), as a general downlink/uplink signaltransmission procedure. Control information transmitted from the UE tothe BS is referred to as uplink control information (UCI). The UCIincludes hybrid automatic repeat and requestacknowledgement/negative-acknowledgement (HARQ-ACK/NACK), schedulingrequest (SR), channel state information (CSI), etc. The CSI includes achannel quality indicator (CQI), a precoding matrix indicator (PMI), arank indicator (RI), etc. While the UCI is transmitted on a PUCCH ingeneral, the UCI may be transmitted on a PUSCH when control informationand traffic data need to be simultaneously transmitted. In addition, theUCI may be aperiodically transmitted through a PUSCH according torequest/command of a network.

FIG. 2 illustrates a radio frame structure. Uplink/downlink data packettransmission is performed on a subframe-by-subframe basis. A subframe isdefined as a predetermined time interval including a plurality ofsymbols. 3GPP LTE supports a type-1 radio frame structure applicable tofrequency division duplex (FDD) and a type-2 radio frame structureapplicable to time division duplex (TDD).

FIG. 2(a) illustrates a type-1 radio frame structure. A downlinksubframe includes 10 subframes each of which includes 2 slots in thetime domain. A time for transmitting a subframe is defined as atransmission time interval (TTI). For example, each subframe has aduration of 1 ms and each slot has a duration of 0.5 ms. A slot includesa plurality of OFDM symbols in the time domain and includes a pluralityof resource blocks (RBs) in the frequency domain. Since downlink usesOFDM in 3GPP LTE, an OFDM symbol represents a symbol period. The OFDMsymbol may be called an SC-FDMA symbol or symbol period. An RB as aresource allocation unit may include a plurality of consecutivesubcarriers in one slot.

The number of OFDM symbols included in one slot may depend on cyclicprefix (CP) configuration. CPs include an extended CP and a normal CP.When an OFDM symbol is configured with the normal CP, for example, thenumber of OFDM symbols included in one slot may be 7. When an OFDMsymbol is configured with the extended CP, the length of one OFDM symbolincreases, and thus the number of OFDM symbols included in one slot issmaller than that in case of the normal CP. In case of the extended CP,the number of OFDM symbols allocated to one slot may be 6. When achannel state is unstable, such as a case in which a UE moves at a highspeed, the extended CP can be used to reduce inter-symbol interference.

When the normal CP is used, one subframe includes 14 OFDM symbols sinceone slot has 7 OFDM symbols. The first three OFDM symbols at most ineach subframe can be allocated to a PDCCH and the remaining OFDM symbolscan be allocated to a PDSCH.

FIG. 2(b) illustrates a type-2 radio frame structure. The type-2 radioframe includes 2 half frames. Each half frame includes 4(5) normalsubframes and 10 special subframes. The normal subframes are used foruplink or downlink according to UL-DL configuration. A subframe iscomposed of 2 slots.

Table 1 shows subframe configurations in a radio frame according toUL-DL configurations.

TABLE 1 Downlink- to-Uplink Uplink- Switch downlink point Subframenumber configuration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U DS U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms  DS U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D D DD D 6 5 ms D S U U U D S U U D

In Table 1, D denotes a downlink subframe, U denotes an uplink subframeand S denotes a special subframe. The special subframe includes DwPTS(Downlink Pilot TimeSlot), GP (Guard Period), and UpPTS (Uplink PilotTimeSlot). DwPTS is used for initial cell search, synchronization orchannel estimation in a UE and UpPTS is used for channel estimation in aBS and uplink transmission synchronization in a UE. The GP eliminates ULinterference caused by multi-path delay of a DL signal between a UL anda DL.

The radio frame structure is merely exemplary and the number ofsubframes included in the radio frame, the number of slots included in asubframe, and the number of symbols included in a slot can be vary.

FIG. 3 illustrates a resource grid of a downlink slot.

Referring to FIG. 3, a downlink slot includes a plurality of OFDMsymbols in the time domain. While one downlink slot may include 7 OFDMsymbols and one resource block (RB) may include 12 subcarriers in thefrequency domain in the figure, the present invention is not limitedthereto. Each element on the resource grid is referred to as a resourceelement (RE). One RB includes 12×7 REs. The number NRB of RBs includedin the downlink slot depends on a downlink transmit bandwidth. Thestructure of an uplink slot may be same as that of the downlink slot.

FIG. 4 illustrates a downlink subframe structure.

Referring to FIG. 4, a maximum of three (four) OFDM symbols located in afront portion of a first slot within a subframe correspond to a controlregion to which a control channel is allocated. The remaining OFDMsymbols correspond to a data region to which a physical downlink sharedchancel (PDSCH) is allocated. A basic resource unit of the data regionis an RB. Examples of downlink control channels used in LTE include aphysical control format indicator channel (PCFICH), a physical downlinkcontrol channel (PDCCH), a physical hybrid ARQ indicator channel(PHICH), etc. The PCFICH is transmitted at a first OFDM symbol of asubframe and carries information regarding the number of OFDM symbolsused for transmission of control channels within the subframe. The PHICHis a response of uplink transmission and carries a HARQ acknowledgment(ACK)/negative-acknowledgment (NACK) signal. Control informationtransmitted through the PDCCH is referred to as downlink controlinformation (DCI). The DCI includes uplink or downlink schedulinginformation or an uplink transmit power control command for an arbitraryUE group.

Control information transmitted through the PDCCH is referred to asdownlink control information (DCI). Formats 0, 3, 3A and 4 for uplinkand formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B and 2C for downlink are definedas DCI formats. Information field type, the number of informationfields, the number of bits of each information field, etc. depend on DICformat. For example, the DCI formats selectively include informationsuch as hopping flag, RB assignment, MCS (Modulation Coding Scheme), RV(Redundancy Version), NDI (New Data Indicator), TPC (Transmit PowerControl), HARQ process number, PMI (Precoding Matrix Indicator)confirmation as necessary. Accordingly, the size of control informationmatched to a DCI format depends on the DCI format. An arbitrary DCIformat may be used to transmit two or more types of control information.For example, DIC formats 0/1A is used to carry DCI format 0 or DICformat 1, which are discriminated from each other using a flag field.

A PDCCH may carry a transport format and a resource allocation of adownlink shared channel (DL-SCH), resource allocation information of anuplink shared channel (UL-SCH), paging information on a paging channel(PCH), system information on the DL-SCH, information on resourceallocation of an upper-layer control message such as a random accessresponse transmitted on the PDSCH, a set of Tx power control commands onindividual UEs within an arbitrary UE group, a Tx power control command,information on activation of a voice over IP (VoIP), etc. A plurality ofPDCCHs can be transmitted within a control region. The UE can monitorthe plurality of PDCCHs. The PDCCH is transmitted on an aggregation ofone or several consecutive control channel elements (CCEs). The CCE is alogical allocation unit used to provide the PDCCH with a coding ratebased on a state of a radio channel. The CCE corresponds to a pluralityof resource element groups (REGs). A format of the PDCCH and the numberof bits of the available PDCCH are determined by the number of CCEs. TheBS determines a PDCCH format according to DCI to be transmitted to theUE, and attaches a cyclic redundancy check (CRC) to control information.The CRC is masked with a unique identifier (referred to as a radionetwork temporary identifier (RNTI)) according to an owner or usage ofthe PDCCH. If the PDCCH is for a specific UE, a unique identifier (e.g.,cell-RNTI (C-RNTI)) of the UE may be masked to the CRC. Alternatively,if the PDCCH is for a paging message, a paging identifier (e.g.,paging-RNTI (P-RNTI)) may be masked to the CRC. If the PDCCH is forsystem information (more specifically, a system information block(SIB)), a system information RNTI (SI-RNTI) may be masked to the CRC.When the PDCCH is for a random access response, a random access-RNTI(RA-RNTI) may be masked to the CRC.

The PDCCH carries a message known as DCI which includes resourceassignment information and other control information for a UE or UEgroup. In general, a plurality of PDCCHs can be transmitted in asubframe. Each PDCCH is transmitted using one or more CCEs. Each CCEcorresponds to 9 sets of 4 REs. The 4 REs are referred to as an REG. 4QPSK symbols are mapped to one REG. REs allocated to a reference signalare not included in an REG, and thus the total number of REGs in OFDMsymbols depends on presence or absence of a cell-specific referencesignal. The concept of REG (i.e. group based mapping, each groupincluding 4 REs) is used for other downlink control channels (PCFICH andPHICH). That is, REG is used as a basic resource unit of a controlregion. 4 PDCCH formats are supported as shown in Table 2.

TABLE 2 PDCCH Number of Number of Number of PDCCH format CCEs (n) REGsbits 0 1 9 72 1 2 8 144 2 4 36 288 3 5 72 576

CCEs are sequentially numbered. To simplify a decoding process,transmission of a PDCCH having a format including n CCEs can be startedusing as many CCEs as a multiple of n. The number of CCEs used totransmit a specific PDCCH is determined by a BS according to channelcondition. For example, if a PDCCH is for a UE having a high-qualitydownlink channel (e.g. a channel close to the BS), only one CCE can beused for PDCCH transmission. However, for a UE having a poor channel(e.g. a channel close to a cell edge), 8 CCEs can be used for PDCCHtransmission in order to obtain sufficient robustness. In addition, apower level of the PDCCH can be controlled according to channelcondition.

LTE defines CCE positions in a limited set in which PDCCHs can bepositioned for each UE. CCE positions in a limited set that the UE needsto monitor in order to detect the PDCCH allocated thereto may bereferred to as a search space (SS). In LTE, the SS has a size dependingon PDCCH format. A UE-specific search space (USS) and a common searchspace (CSS) are separately defined. The USS is set per UE and the rangeof the CSS is signaled to all UEs. The USS and the CSS may overlap for agiven UE. In the case of a considerably small SS with respect to aspecific UE, when some CCEs positions are allocated in the SS, remainingCCEs are not present. Accordingly, the BS may not find CCE resources onwhich PDCCHs will be transmitted to available UEs within givensubframes. To minimize the possibility that this blocking continues tothe next subframe, a UE-specific hopping sequence is applied to thestarting point of the USS.

Table 3 shows sizes of the CSS and USS.

TABLE 3 Number of Number of candidates in candidates in PDCCH Number ofcommon search dedicated search format CCEs (n) space space 0 1 — 6 1 2 —6 2 4 4 2 3 8 2 2

To control computational load of blind decoding based on the number ofblind decoding processes to an appropriate level, the UE is not requiredto simultaneously search for all defined DCI formats. In general, the UEsearches for formats 0 and 1A at all times in the USS. Formats 0 and 1Ahave the same size and are discriminated from each other by a flag in amessage. The UE may need to receive an additional format (e.g. format 1,1B or 2 according to PDSCH transmission mode set by a BS). The UEsearches for formats 1A and 1C in the CSS. Furthermore, the UE may beset to search for format 3 or 3A. Formats 3 and 3A have the same size asthat of formats 0 and 1A and may be discriminated from each other byscrambling CRC with different (common) identifiers rather than aUE-specific identifier. PDSCH transmission schemes and informationcontent of DCI formats according to transmission mode (TM) are arrangedbelow.

Transmission mode (TM)

-   -   Transmission mode 1: Transmission from a single base station        antenna port    -   Transmission mode 2: Transmit diversity    -   Transmission mode 3: Open-loop spatial multiplexing    -   Transmission mode 4: Closed-loop spatial multiplexing    -   Transmission mode 5: Multi-user MIMO (Multiple Input Multiple        Output)    -   Transmission mode 6: Closed-loop rank-1 precoding    -   Transmission mode 7: Single-antenna port (ports) transmission    -   Transmission mode 8: Double layer transmission (ports 7 and 8)        or single-antenna port (port 7 or 8) transmission    -   Transmission mode 9: Transmission through up to 8 layers (ports        7 to 14) or single-antenna port (port 7 or 8) transmission

DCI Format

-   -   Format 0: Resource grants for PUSCH transmission    -   Format 1: Resource assignments for single codeword PDSCH        transmission (transmission modes 1, 2 and 7)    -   Format 1A: Compact signaling of resource assignments for single        codeword PDSCH (all modes)    -   Format 1B: Compact resource assignments for PDSCH using rank-1        closed loop precoding (mod 6)    -   Format 1C: Very compact resource assignments for PDSCH (e.g.        paging/broadcast system information)    -   Format 1D: Compact resource assignments for PDSCH using        multi-user MIMO (mode 5)    -   Format 2: Resource assignments for PDSCH for closed-loop MIMO        operation (mode 4)    -   Format 2A: Resource assignments for PDSCH for open-loop MIMO        operation (mode 3)    -   Format 3/3A: Power control commands for PUCCH and PUSCH with        2-bit/1-bit power adjustments

FIG. 5 illustrates an EPDCCH. The EPDCCH is a channel additionallyintroduced in LTE-A.

Referring to FIG. 5, a PDCCH (for convenience, legacy PDCCH or L-PDCCH)according to legacy LTE may be allocated to a control region (see FIG.4) of a subframe. In the figure, the L-PDCCH region means a region towhich a legacy PDCCH may be allocated. Meanwhile, a PDCCH may be furtherallocated to the data region (e.g., a resource region for a PDSCH). APDCCH allocated to the data region is referred to as an E-PDCCH. Asshown, control channel resources may be further acquired via the E-PDCCHto mitigate a scheduling restriction due to restricted control channelresources of the L-PDCCH region. Similarly to the L-PDCCH, the E-PDCCHcarries DCI. For example, the E-PDCCH may carry downlink schedulinginformation and uplink scheduling information. For example, the UE mayreceive the E-PDCCH and receive data/control information via a PDSCHcorresponding to the E-PDCCH. In addition, the UE may receive theE-PDCCH and transmit data/control information via a PUSCH correspondingto the E-PDCCH. The E-PDCCH/PDSCH may be allocated starting from a firstOFDM symbol of the subframe, according to cell type. In thisspecification, the PDCCH includes both L-PDCCH and EPDCCH unlessotherwise noted.

FIG. 6 illustrates a structure of an uplink subframe used in LTE(-A).

Referring to FIG. 6, a subframe 500 is composed of two 0.5 ms slots 501.Assuming a length of a normal cyclic prefix (CP), each slot is composedof 7 symbols 502 and one symbol corresponds to one SC-FDMA symbol. Aresource block (RB) 503 is a resource allocation unit corresponding to12 subcarriers in the frequency domain and one slot in the time domain.The structure of the uplink subframe of LTE(-A) is largely divided intoa data region 504 and a control region 505. A data region refers to acommunication resource used for transmission of data such as voice, apacket, etc. transmitted to each UE and includes a physical uplinkshared channel (PUSCH). A control region refers to a communicationresource for transmission of an uplink control signal, for example,downlink channel quality report from each UE, reception ACK/NACK for adownlink signal, uplink scheduling request, etc. and includes a physicaluplink control channel (PUCCH). A sounding reference signal (SRS) istransmitted through an SC-FDMA symbol that is lastly positioned in thetime axis in one subframe. SRSs of a plurality of UEs, which aretransmitted to the last SC-FDMAs of the same subframe, can bedifferentiated according to frequency positions/sequences. The SRS isused to transmit an uplink channel state to an eNB and is periodicallytransmitted according to a subframe period/offset set by a higher layer(e.g., RRC layer) or aperiodically transmitted at the request of theeNB.

FIG. 7 illustrates SC-FDMA and OFDMA schemes. The 3GPP system employsOFDMA in downlink and uses SC-FDMA in uplink.

Referring to FIG. 7, both a UE for transmitting an uplink signal and aBS for transmitting a downlink signal include a serial-to-parallelconverter 401, a subcarrier mapper 403, an M-point IDFT module 404, anda cyclic prefix (CP) adder 406. The UE for transmitting a signalaccording to SC-FDMA additionally includes an N-point DFT module 402.

Next, HARQ (Hybrid Automatic Repeat reQuest) will be described. Whenthere are a plurality of UEs having data to be transmitted onuplink/downlink in a wireless communication, an eNB selects UEs whichwill transmit data per transmission time internal (TTI) (e.g.,subframe). In a system using multiple carriers and the like, an eNBselects UEs which will transmit data on uplink/downlink per TTI and alsoselects a frequency band to be used for data transmission of thecorresponding UEs.

When description is based on uplink (UL), UEs transmit reference signals(or pilot signals) on uplink and an eNB detects channel states of theUEs using the reference signals transmitted from the UEs and selects UEswhich will transmit data on uplink in each unit frequency band per TTI.The eNB notifies the UEs of the result of selection. That is, the eNBtransmits, to UL scheduled UEs, a UL assignment message indicating thatthe UEs may transmit data using a specific frequency band in a specificTTI. The UL assignment message is also referred to as a UL grant. TheUEs transmit data on uplink according to the UL assignment message. TheUL assignment message may include UE identity (ID), RB allocationinformation, a modulation and coding scheme (MCS), a redundancy version(RV), new data indication (NDI) and the like.

In the case of synchronous HARQ, a retransmission time is appointed inthe system (e.g., after 4 subframes from a NACK reception time)(synchronous HARQ). Accordingly, the eNB may send a UL grant message toUEs only in initial transmission and subsequent retransmission isperformed according to an ACK/NACK signal (e.g., PHICH signal). In thecase of asynchronous HARQ, a retransmission time is not appointed andthus the eNB needs to send a retransmission request message to UEs.Further, frequency resources or an MCS for retransmission are identicalto those in previous transmission in the case of non-adaptive HARQ,whereas frequency resources or an MCS for retransmission may differ fromthose in previous transmission in the case of adaptive HARQ. Forexample, in the case of asynchronous adaptive HARQ, the retransmissionrequest message may include UE ID, RB allocation information, HARQprocess ID/number, RV and NDI information because frequency resources oran MCS for retransmission vary with transmission time.

FIG. 8 illustrates a UL HARQ operation in an LTE(-A) system. In theLTE(-A) system, asynchronous adaptive HARQ is used as UL HARQ. When8-channel HARQ is used, 0 to 7 are provided as HARQ process numbers. OneHARQ process operates per TTI (e.g., subframe). Referring to FIG. 8, aUL grant is transmitted to a UE 120 through a PDCCH (S600). The UE 120transmits UL data to an eNB 110 after 4 subframes from the time (e.g.,subframe 0) at which the UL grant is received using an RB and an MCSdesignated by the UL grant (S602). The eNB 110 decodes the UL datareceived from the UE 120 and then generates ACK/NACK. When decoding ofthe UL data fails, the eNB 110 transmits NACK to the UE 120 (S604). TheUE 120 retransmits the UL data after 4 subframes from the time at whichNACK is received (S606). Initial transmission and retransmission of theUL data are performed through the same HARQ process (e.g., HARQ process4). ACK/NACK information may be transmitted through a PHICH.

Scheduling for UL transmission in LTE is enabled only if UL transmissiontiming of a user equipment is synchronized. A random access procedure isused for various usages. For instance, a random access procedure isperformed in case of an initial network access, a handover, a dataoccurrence or the like. A user equipment may be able to obtain ULsynchronization via the random access procedure. Once the ULsynchronization is obtained, a base station may be able to allocate aresource for UL transmission to the corresponding user equipment. Therandom access procedure may be classified into a contention basedprocedure and a non-contention based procedure.

FIG. 9 is a diagram for one example of a contention based random accessprocedure.

Referring to FIG. 9, a user equipment receives information on a randomaccess from a base station via system information. Thereafter, if therandom access is required, the user equipment transmits a random accesspreamble (or a message 1) to the base station [S710]. Once the basestation receives the random access preamble from the user equipment, thebase station sends a random access response message (or, a message 2) tothe user equipment [S720]. In particular, a DL scheduling information onthe random access response message may be transmitted on L1/L2 controlchannel (PDCCH) by being CRC masked with RA-RNTI (random access-RNTI).Having received the RA-RNTI masked DL scheduling signal, the userequipment receives the random access response message on PDSCH and maybe then able to decode the received random access response message.Subsequently, the user equipment checks whether a random access responseinformation indicated to the user equipment is included in the receivedrandom access response message. In doing so, a presence or non-presenceof the random access response information indicated to the userequipment may be checked in a manner of checking whether RAID (randomaccess preamble ID) for the preamble having transmitted by the userequipment is present or not. The random access response information mayinclude a timing advance indicating a timing offset information forsynchronization, a radio resource allocation information on a resourceused in UL, a temporary identifier (e.g., T-RNTI) for user equipment(UE) identification and the like. Once the random access responseinformation is received, the user equipment sends a UL message (or, amessage 3) on UL SCH (uplink shared channel) in accordance with theradio resource allocation information included in the received randomaccess response information [S730]. Having received the UL message fromthe user equipment in the step S730, the base station sends a contentionresolution message (or, a message 4) to the user equipment [S740].

FIG. 10 is a diagram for one example of a non-contention based randomaccess procedure. A non-contention based random access procedure may beused in a handover procedure or may exist if requested by an order givenby a base station. A basic procedure is as good as a contention basedrandom access procedure.

Referring to FIG. 10, a user equipment receives assignment of a randomaccess preamble (i.e., a dedicated random access preamble) for the userequipment only from a base station [S810]. A dedicated random accesspreamble indication information (e.g., a preamble index) may be includedin a handover command message or may be received on PDCCH. The userequipment transmits the dedicated random access preamble to the basestation [S820]. Thereafter, the user equipment receives a random accessresponse from the base station [S830] and the random access procedure isended.

In order to indicate a non-contention based random access procedure witha PDCCH order, DCI format 1A is used. And, the DCI format 1A may be usedfor compact scheduling for one PDSCH codeword. The following informationis transmitted using the DCI format 1A.

-   -   Flag for identifying DCI format 0 or DCI format 1A: This flag is        1-bit flag. A flag value ‘0’ indicates DCI format 0 and a flag        value ‘1’ indicates DCI format 1A.

If all the fields remaining after scrambling CRC of DCI format 1A withC-RNTI are set as follows, the DCI format 1A may be used for a randomaccess procedure according to a PDCCH order.

-   -   Localized/distributed VRB (virtual resource block) assignment        flag: This flag is 1-bit flag. This flag is set to 0.    -   Resource block assignment information: ┌log₂(N_(RB) ^(DL)(N_(RB)        ^(DL)+1)/2)┐. Every bit is set to 1.    -   Preamble index: 6 bits    -   PRACH mask index: 4 bits    -   All the remaining bits for compact scheduling of PDSCH in DCI        format 1A are set to 0.

FIG. 11 illustrates uplink-downlink frame timing relation.

Referring to FIG. 11, transmission of the uplink radio frame number istarts prior to (N_(TA)+N_(TAoffset))*T_(s) seconds from the start ofthe corresponding downlink radio frame. In case of the LTE system,0≤N_(TA)≤20512, N_(TAoffset)=0 in FDD, and N_(TAoffset)=624 in TDD. Thevalue N_(Taoffset) is a value in advance recognized by the BS and theUE. If N_(TA) is indicated through a timing advance command during arandom access procedure, the UE adjusts transmission timing of UL signal(e.g., PUCCH/PUSCH/SRS) through the above equation. UL transmissiontiming is set to multiples of 16 T_(s). The timing advance commandindicates the change of the UL timing based on the current UL timing.The timing advance command T_(A) within the random access response is a11-bit timing advance command, and indicates values of 0, 1, 2, . . . ,1282 and a timing adjustment value is given by N_(TA)=T_(A)*16. In othercases, the timing advance command T_(A) is a 6-bit timing advancecommand, and indicates values of 0, 1, 2, . . . , 63 and a timingadjustment value is given by N_(TA,new)=N_(TA,old)+(T_(A)−31)*16. Thetiming advance command received at subframe n is applied from thebeginning of subframe n+6. In case of FDD, as shown, transmitting timingof UL subframe n is advanced based on the start time of the DL subframen. On the contrary, in case of TDD, transmitting timing of UL subframe nis advanced based on the end time of the DL subframe n+1 (not shown).

FIG. 12 illustrates carrier aggregation (CA) communication system.

Referring to FIG. 12, a plurality of UL/DL component carriers (CCs) canbe aggregated to support a wider UL/DL bandwidth. The CCs may becontiguous or non-contiguous in the frequency domain. Bandwidths of theCCs can be independently determined. Asymmetrical CA in which the numberof UL CCs is different from the number of DL CCs can be implemented.Control information may be transmitted/received only through a specificCC. This specific CC may be referred to as a primary CC and other CCsmay be referred to as secondary CCs. For example, when cross-carrierscheduling (or cross-CC scheduling) is applied, a PDCCH for downlinkallocation can be transmitted on DL CC #0 and a PDSCH correspondingthereto can be transmitted on DL CC #2. The term “component carrier” maybe replaced by other equivalent terms (e.g. “carrier”, “cell”, etc.).

For cross-CC scheduling, a carrier indicator field (CIF) is used.Presence or absence of the CIF in a PDCCH can be determined by higherlayer signaling (e.g. RRC signaling) semi-statically and UE-specifically(or UE group-specifically). The baseline of PDCCH transmission issummarized as follows.

-   -   CIF disabled: a PDCCH on a DL CC is used to allocate a PDSCH        resource on the same DL CC or a PUSCH resource on a linked UL        CC.    -   No CIF    -   CIF enabled: a PDCCH on a DL CC can be used to allocate a PDSCH        or PUSCH resource on a specific DL/UL CC from among a plurality        of aggregated DL/UL CCs using the CIF.    -   LTE DCI format extended to have CIF    -   CIF corresponds to a fixed x-bit field (e.g. x=3) (when CIF is        set)    -   CIF position is fixed irrespective of DIC format size (when CIF        is set)

When the CIF is present, the BS may allocate a monitoring DL CC (set) toreduce BD complexity of the UE. For PDSCH/PUSCH scheduling, the UE maydetect/decode a PDCCH only on the corresponding DL CCs. The BS maytransmit the PDCCH only through the monitoring DL CC (set). Themonitoring DL CC set may be set UE-specifically, UE-group-specificallyor cell-specifically.

FIG. 13 illustrates scheduling when a plurality of carriers isaggregated. It is assumed that 3 DL CCs are aggregated and DL CC A isset to a PDCCH CC. DL CC A˜C may be referred to as a serving CC, servingcarrier, serving cell, etc. When the CIF is disabled, each DL CC cantransmit only a PDCCH that schedules a PDSCH corresponding to the DL CCwithout a CIF according to LTE PDCCH rule (non-cross-CC scheduling).When the CIF is enabled through UE-specific (or UE-group-specific orcell-specific) higher layer signaling, a specific CC (e.g. DL CC A) cantransmit not only the PDCCH that schedules the PDSCH of DL CC A but alsoPDCCHs that schedule PDSCHs of other DL CCs using the CIF(cross-scheduling). A PDCCH is not transmitted on DL CC B and DL CC C.

Furthermore, in a millimeter wave (mmW) system, a wavelength of a signalis short, so that a multitude of antennas can be installed in the samearea. For example, since the wavelength is 1 cm in a 30 GHz band, atotal of 100 antenna elements can be installed in a 5-by-5 cm² panel ina form of a two-dimensional array with a 0.5λ (wavelength) spacing.Therefore, in the mmW system, a plurality of antenna elements are usedto increase a beamforming (BF) gain to increase a coverage or increase athroughput.

In this connection, when each antenna element has a TXRU (transceiverunit) so that transmission power and phase can be adjusted for eachantenna element, independent beamforming may be realized for eachfrequency resource. However, installing each TXRU in each of all 100antenna elements is ineffective in terms of cost. Therefore, a scheme ofmapping a plurality of antenna elements to one TXRU and adjusting adirection of the beam with an analog phase shifter is considered. Thisanalog beamforming scheme may form only one beam direction in a fullband, and has a disadvantage that a frequency selective beam cannot beachieved. Thus, as an intermediate form between digital BF and analogBF, a hybrid BF in which B TXRUs map to Q antenna elements (B<Q) may beconsidered. In this case, a number of directions of a beam in which thebeam is simultaneously transmitted is limited to a number smaller thanor equal to B, though it varies depending on a connection scheme betweenthe B TXRUs and Q antenna elements.

FIG. 14 illustrates analog beamforming. Referring to FIG. 14, atransmitter may transmit a signal while changing a direction of the beamover time (transmit beamforming). A receiver may also receive a signalwhile changing a direction of the beam over time (receive beamforming).Within a certain time interval, (i) directions of the transmit andreceive beams may change simultaneously over time, (ii) a direction ofthe transmit beam may be fixed over time, while only a direction of thereceive beam may change over time, or (iii) a direction of the receivebeam may be fixed over time, while only a direction of the transmit beammay change over time.

In next-generation RAT (Radio Access Technology), a self-containedsubframe is considered in order to minimize data transmission latency.FIG. 15 illustrates a self-contained subframe structure. In FIG. 15, ahatched region represents a DL control region and a black regionrepresents a UL control region. A blank region may be used for DL datatransmission or UL data transmission. DL transmission and ULtransmission are sequentially performed in a single subframe, and thusDL data can be transmitted and UL ACK/NACK can also be received in asubframe. Consequently, a time taken until data retransmission isperformed when a data transmission error is generated is reduced andthus final data delivery latency can be minimized.

As examples of self-contained subframe types which can beconfigured/set, the following four subframe types can be considered.Respective periods are arranged in a time sequence.

-   -   DL control period+DL data period+GP (Guard Period)+UL control        period    -   DL control period+DL data period    -   DL control period+GP+UL data period+UL control period    -   DL control period+GP+UL data period

A PDFICH, a PHICH and a PDCCH can be transmitted in the data controlperiod and a PDSCH can be transmitted in the DL data period. A PUCCH canbe transmitted in the UL control period and a PUSCH can be transmittedin the UL data period. The GP provides a time gap in a process in whicha BS and a UE switch from a transmission mode to a reception mode or ina process in which the BS and the UE switch from the reception mode tothe transmission mode. Some OFDM symbols in a subframe at a time when DLswitches to UL may be set to the GP.

Embodiment

In New RAT (NR) system environment, when CA is performed on a pluralityof cells for a single UE, OFDM numerology (e.g., subcarrier spacing andOFDM symbol period based on the subcarrier spacing) and a beamformingoperation (e.g., TX/RX (analog or hybrid beamforming) to be applied andbeam tracking) can be differently configured used based on a cell(group). In the abovementioned CA situation, it is necessary to considera HARQ operation related to DL/UL data scheduling/transmission, a powercontrol scheme in UL, a beam-related information signaling method, aUE-common signal transmission mechanism, and the like.

[1] Method of Transmitting UL Control Channel on which UCI is Carried

In NR system environment, a UE capable of performing a UL CA operationand a UE incapable of performing the UL CA operation may coexistdepending on implementation and capability of a UE. Although a UE isable to perform a UL CA operation, UL transmission performance of the UEperformed via a plurality of cells can be degraded due to such a factoras UL coverage, power limitation, and the like. It may consider two ULcontrol channel (on which UCI is carried) transmission modes in CAsituation in consideration of the factors. Specifically, 1) a UE cantransmit a UL control channel through a specific cell (e.g., PCell) onlyor 2) a UE can be configured to individually transmit a UL controlchannel according to a cell. For clarity, although HARQ-ACK (i.e., A/N),which is transmitted in response to received DL data, is mainlyexplained, the same principle can also be applied to different UCI suchas CSI, SR, and the like.

(a) Mode 1: UL Control Channel on PCell Only

In the mode 1, it is able to transmit a plurality of A/N feedbacks(“multi-cell A/N”) via a specific cell (e.g., PCell) only in response toDL data received in a plurality of cells. Alt 1) the multi-cell A/N canbe configured to be transmitted via a single UL control channel resourceonly or Alt 2) the multi-cell A/N can be configured to be transmittedvia a plurality of UL control channel resources. In case of the Alt 2,a) it may be able to configure each of a plurality of the UL controlchannel resources to transmit A/N in response to data received in a cellonly or b) it may be able to configure each of a plurality of the ULcontrol channel resources to transmit one or more A/N in response to DLdata received through a cell group (corresponding to a part of theentire cell groups) including one or more cells. In particular, a ULcontrol channel resource for transmitting A/N can be differentlyconfigured/allocated according to a cell (a) or a cell group (b). Hence,(in case of considering an operation of indicating information on a ULcontrol channel resource carrying A/N), it may indicate different ULcontrol channel resource to a cell (a) or a cell group (b) via a DLgrant that performs DL data scheduling.

Meanwhile, in case of transmitting a plurality of CSI feedbacks(“multi-cell CSI”) on DL radio channels of a plurality of cells, it isable to configure a plurality of the CSI feedbacks to be transmitted viaa specific cell (e.g., PCell) only. Alt 1) the multi-cell CSI can beconfigured to be transmitted via a single UL control channel resourceonly or Alt2) the multi-cell CSI can be configured to be transmitted viaa plurality of UL control channel resources. In case of the Alt 2, a) itmay be able to configure each of a plurality of the UL control channelresources to transmit single CSI only for a cell or b) it may be able toconfigure each of a plurality of the UL control channel resources totransmit one or more CSI for a cell group (corresponding to a part ofthe entire cell groups) including one or more cells. In particular, a ULcontrol channel resource for transmitting CSI can be differentlyconfigured/allocated according to a cell (a) or a cell group (b).Meanwhile, it may be able to configure an SR to be transmitted via asingle UL control channel resource or a plurality of UL control channelresources. Specifically, it may consider a method of transmitting aquantized BSR (buffer status report) in a form of multi-bit via a singleUL control channel resource or a plurality of UL control channelresources by quantizing a UL buffer status of a UE using multiple bits.

(B) Mode 2: UL Control Channel on Each Cell

In the mode 2, it may be able to configure A/N (and/or CSI) feedback tobe transmitted via a cell itself in response to DL data received in thecell.

It may be able to semi-statically indicate a mode for performing ULcontrol channel transmission among the mode 1 and the mode 2 (and/or ascheme for performing UL control channel transmission among the Alt 1and the Alt 2) via higher layer signaling (e.g., RRC signaling). Or, itmay be able to dynamically indicate a mode for performing UL controlchannel transmission among the mode 1 and the mode 2 via L1 signaling(e.g., DL control channel transmission). And, whether or not the mode2-based UL control channel transmission operation (and/or the Alt2-based UL control channel transmission operation of the mode 1) isavailable may become UE capability which varies according to UEimplementation. A UE can report information on the capability to an eNBat appropriate timing (e.g., initial access or RRC connection stage).

Meanwhile, it may be able to set the same UL control channeltransmission mode (or, Alt schemes in the mode 1) to different UCI(e.g., A.N and CSI). Or, it may be able to independently (differently)configure a UL control channel transmission mode (or, Alt schemes in themode 1) according to UCI.

FIG. 16 illustrates a UCI transmission procedure according to the mode 1and FIG. 17 illustrates a UCI transmission procedure according to themode 2. Referring to FIG. 16, a UE receives multiple DL data frommultiple cells and is able to transmit a plurality of A/N feedbacks(“multi-cell A/N”) via a specific cell (e.g., PCell) only in response toDL data received in a plurality of cells. Alt 1) the multi-cell A/N canbe configured to be transmitted via a single UL control channel resourceonly or Alt 2) the multi-cell A/N can be configured to be transmittedvia a plurality of UL control channel resources. FIG. 16 illustrates aprocedure of transmitting multi-cell A/N according to the Alt 2.Referring to FIG. 17, a UE receives multiple DL data from multiple cellsand is able to transmit A/N (and/or CSI) feedback via a cell itself inresponse to DL data received in the cell.

[2] CA Scheme Between Different OFDM Numerologies

In NR system environment, it may be able to differently configure OFDMnumerology (e.g., subcarrier spacing and OFDM symbol (i.e., OS) durationbased on the subcarrier spacing) among a plurality of cells carrieraggregated on a single UE. Hence, in the aspect of a single UE,(absolute time) duration of an SF or a TTI (for clarity, commonlyreferred to as SF) can be differently configured between aggregatedcells. In consideration of this, in a CA situation between cells havinga different SCS and OS duration, it may consider an operation methoddescribed in the following for a DL/UL data-related HARQ procedure(e.g., when DL/UL data transmission in an SCell is cross-CC scheduledfrom a PCell, A/N feedback is transmitted via the PCell in response toDL data received in the SCell.) In a CA situation between cells havingthe same SCS and OS duration, although duration of an SF or a TTI isdifferently configured between the cells, the same principle can beapplied.

(A) Cross-CC Scheduling Between Different SCS

FIG. 18 illustrates a case that a cell X having a big SCS (i.e., shortOS duration or short SF duration) is configured to be scheduled by acell Y having a small SCS (i.e., long OS duration or long SF duration).Referring to FIG. 18, DL/UL data transmission in the K (K>1) SFs of thecell X can be configured to be scheduled by one SF of the cell Y. Inthis case, a single SF of the cell Y and the K SFs of the cell X mayhave the same time duration. Specifically, Opt 1) when a DL/UL grant forscheduling the (maximum) K SFs of the cell X is transmitted/detected atthe same time via a DL control channel transmission region (within asingle SF) of the cell Y or Opt 2) when the K DL control channeltransmission regions within a single SF of the cell Y is independentlyconfigured, it is able to transmit/detect a DL/UL grant for scheduling adifferent SF in the cell X via each region.

FIG. 19 illustrates a case that a cell X having a small SCS (i.e., longOS duration or long SF duration) is configured to be scheduled by a cellY having a big SCS (i.e., short OS duration or short SF duration).Referring to FIG. 19, DL/UL data transmission in a single SF of the cellX can be configured to be scheduled by all or a part (e.g., 1 SF) of theN (N>1) SFs of the cell Y. In this case, the N SFs of the cell Y and asingle SF of the cell X may have the same time duration. Specifically,Opt 1) a DL/UL grant for scheduling a single SF of the cell X istransmitted/detected via an SF belonging to a plurality of SFs (i.e., SFgroup) corresponding to all or a part of the N SFs of the cell Y (FIG.19 (a)), or Opt 2) a DL/UL grant for scheduling an SF of the cell X canbe transmitted/detected via a specific SF (e.g., an SF of the cell Yoverlapped with a first OS within an SF of the cell X over time) amongthe N SFs of the cell Y (FIG. 19 (b)). Meanwhile, in case of the Opt 1,SF timing at which a DL/UL grant is transmitted within an SF group mayvary and each of a DL grant and a UL grant can be transmitted via adifferent SF within an SF group. Hence, a UE can sequentially perform ablind decoding operation on DL control channel transmission regions ofall SFs belonging to an SF group of the cell Y. If all DL/UL grants forthe cell X are detected within an SF group of the cell Y, the UE may notperform the blind decoding operation on DL control channel transmissionregions within the remaining SFs.

(B) HARQ-ACK Timing for CA with Different SCS

In the CA situation of NR system, SCS or OS duration (or TTI length) canbe differently configured between a cell (e.g., SCell) in which DL datais transmitted and a cell (e.g., PCell) in which A/N feedback istransmitted in response to the DL data. In this case, Opt 1) A/N timing(e.g., delay between DL data reception and A/N transmission) can beconfigured on the basis of a TTI length of the SCell in which the DLdata is transmitted or Opt 2) the A/N timing can be configured on thebasis of a TTI length of the PCell in which the A/N feedback istransmitted (e.g., A/N timing (candidate set) is configured by amultiple of the TTI length of the PCell). For clarity, the A/N timingconfigured according to the Opt 1/2 is referred to as ‘temp A/N timing”.In case of the Opt 1, actually applied actual A/N timing of the PCellcan be determined by timing overlapped with timing appearing after thetemp A/N timing (e.g., time corresponding to the N SCell TTIs) from thetiming at which the DL data is received or a first TTI (or UL controlchannel transmission (for A/N)) duration) of the PCell appearing afterthe temp A/N timing from the DL data reception timing of the SCell.Meanwhile, in case of the Opt 2, actually applied actual A/N timing ofthe PCell can be determined by timing overlapped with timing at whichthe DL data is received or a TTI (or UL control channel transmission(for A/N)) duration of the PCell appearing after the temp A/N timing(e.g., time corresponding to the M PCell TTIs) from the first TTI (or ULcontrol channel transmission (for A/N)) duration of the PCell existingafter the DL data reception timing of the SCell.

Meanwhile, in case of UL HARQ, SCS or OS duration (or a TTI length) canbe differently configured between a cell (e.g., PCell) in which a ULgrant is transmitted and a cell (e.g., SCell) in which UL data istransmitted in response to the UL grant. In this case, Opt 1) HARQtiming (e.g., delay between UL grant reception and UL data transmission)can be configured on the basis of a TTI length of the SCell in which theUL grant is transmitted (e.g., HARQ timing (candidate set) is configuredby a multiple of a TTI length of the PCell) or Opt 2) the HARQ timingcan be configured on the basis of a TTI length of the SCell in which theUL data is transmitted (e.g., HARQ timing (candidate set) is configuredby a multiple of a TTI length of the SCell). For convenience, the HARQtiming configured according to the Opt 1/2 is referred to as ‘temp HARQtiming’. In case of the Opt 1, actually applied actual HARQ timing ofthe SCell can be determined as a timing overlapped with a timing afterthe tempHARQ timing (e.g., time corresponding to the K PCell TTIs) froma timing at which the UL grant is received on PCell, or an earliest TTI(or UL data channel transmission) duration of the SCell, including thetiming overlapped, appearing thereafter. Meanwhile, in case of the Opt2, actually applied actual HARQ timing of the SCell can be determined asa TTI (or UL data channel transmission) duration after the temp HARQtiming (e.g., time corresponding to the L SCell TTIs) from a timingoverlapped with a timing at which the UL grant is received on PCell oran earliest TTI (or UL data channel transmission) duration of the SCell,including the timing overlapped, appearing thereafter.

(C) UL TA (Timing Advancement) Management Between Different SCS

When CA is performed between cells operating with a different SCS, if TAfor matching UL synchronization is applied, since sample time and a CPlength are also differentiated according to the different SCS, it isdifficult or impossible to apply the same TA value between the cellsoperating with the different SCS. Hence, if a set of one or more cellsto which the same TA value is applicable is defined as a TAG (TimingAdvance Group), it may be able to configure only cells operating withthe same SCS to belong to a TAG It may be able to configure cellsoperating with a different SCS not to belong to the same TAG Inaddition, it may be able to configure only cells operating with the sameSCS and cells operating with the same CP length (a CP length differencebetween cells is equal to or less than a specific level) to belong to aTAG It may be able to configure cells operating with a different SCS ora different CP length (a CP length difference between cells exceeds aspecific level) not to belong to the same TAG Or, it may be able toconfigure cells of which an SCS value difference between cells (and/or aCP length difference between cells) is equal to or less than a specificlevel to belong to a TAG In particular, it may be able to configurecells of which an SCS value difference between cells (and/or a CP lengthdifference between cells) exceeds a specific level not to belong to thesame TAG

As a different method, in a state that there is no separate TAGconfiguration restriction, if cells operating with a different SCS areconfigured to belong to a TAG, it may be able to configure a randomaccess signal for determining a TA value to be transmitted by a celloperating with a biggest SCS (i.e., smallest sample time and CP length)(or a cell configured by the biggest SCS of a random access signal)among the cells belonging to the TAG In addition, it may be able toconfigure a random access signal to be transmitted via a cell to which asmallest CP length is set only among the cells operating with thebiggest SCS (or cells configured by the biggest SCS of a random accesssignal) within the same TAG

When a cell group (UCIG) is configured to transmit a UL control channel(or UL data channel) carrying UCI (e.g., A/N, CSI) on a specific cellset (to which cells belong) via a specific (random) cell of the cell setonly (i.e., a UL control channel carrying UCI on cells belonging to theUCIG is configured to be transmitted via a specific cell of the UCIGonly), the UCIG (and a cell in which UL control channel (UCI) istransmitted) can be configured by applying a condition identical to theTAG (and a cell in which a random access signal is transmitted). And,when a cell group (DCIG) is configured to transmit a DL control channelcarrying DCI (e.g., DL/UL scheduling grant) on a specific cell set (towhich cells belong) via a specific cell of the cell set only (i.e.,cross-CC scheduling is configured to be performed between cellsbelonging to the DCIG only), the DCIG can be configured by applying acondition identical to the TAG In particular, it is able to configurethe DCIG (and a cell in which a DL control channel (DCI) is transmitted)by applying the condition identical to the TAG (and a cell in which arandom access signal is transmitted).

[3] Analog Beam-Forming Considering CA Scheme

In case of an NR system operating on a specific frequency band (e.g.,high carrier frequency), it is highly probable that the NR systemperforms TX/RX (analog or hybrid) beamforming on a DL/UL signal in aneNB (and/or a UE) based on mmW characteristic. As an example, the eNBtransmits a plurality of specific (UE-common) signals (e.g., asynchronization signal or a reference signal) having different beamdirection during a certain period and the UE reports receptionquality/state information (i.e., BSI (beam state information)) and/orpreferred beam information (e.g., beam ID or index) optimized to the UEof a received specific signal (i.e., beam direction) to the eNB. The UEcan perform beamforming-based DL/UL signal transmission/receptionoperation based on the information. In this case, the beam ID (or index)may correspond to an index for identifying a beam (direction) formed bycombination of antenna ports different from each other. Meanwhile, incase of an NR system operating on a specific frequency band (e.g. lowcarrier frequency), it is probable that the NR system operates as alegacy system without applying the abovementioned beamforming. Inparticular, in NR system environment, it may consider a case that CA isperformed on a cell to which beamforming (BF) is applied (i.e., BF cell)and a cell to which beamforming is not applied (i.e., non-BF cell) atthe same time in a UE.

(A) CA Between Non-BF Cell and BF Cell

When CA is performed between a non-BF cell and a BF cell, the non-BFcell may support relatively superior signal transmission reliability andcoverage compared to the BF cell. Hence, in case of a specific (e.g.,important) information type, it may be able to configure transmission tobe performed by the non-BF cell (a UL data/control channel of the cell)only (by preferentially selecting a UL data/control channel of thenon-BF cell (prior to the BF cell)). In this case, the specificinformation type can include at least one selected from the groupconsisting of a response message received from the eNB in response toRRC configuration, a response message received from the eNB in responseto MAC command, various reports (e.g., power headroom report, bufferstatus report) using an (event-trigger and period scheme-based) MACsignal, and an RRM (Radio Resource Management) measurement-relatedreport.

Meanwhile, it may be able to configure either non-BF cells or BF cellsto belong to a single DCIG only. In particular, it may be able toconfigure a non-BF cell and a BF cell not to belong to the same DCIG Or,if a non-BF cell and a BF cell are configured to belong to a single DCIGwithout a separate DCIG configuration restriction, it may be able toconfigure a DL control channel (DCI) to be transmitted via a non-BF cellonly. To this end, it may be able to configure at least one non-BF cellto belong to a DCIG Similarly, it may be able to configure either non-BFcells or BF cells to belong to a single UCIG only. In particular, it maybe able to configure a non-BF cell and a BF cell not to belong to thesame UCIG In this case, if a non-BF cell and a BF cell are configured tobelong to a single UCIG without a separate UCIG configurationrestriction, it may be able to configure a UL control channel (UCI) tobe transmitted via a non-BF cell only. To this end, it may be able toconfigure at least one non-BF cell to belong to a UCIG Additionally, itmay be able to configure either non-BF cells or BF cells to belong to asingle TAG only. In particular, it may be able to configure a non-BFcell and a BF cell not to belong to the same TAG In this case, if anon-BF cell and a BF cell are configured to belong to a single TAGwithout a separate TAG configuration restriction, it may be able toconfigure a random access signal to be transmitted via a non-BF cellonly. To this end, it may be able to configure at least one non-BF cellto belong to a TAG

Meanwhile, the UE can transmit a signal for asking the eNB to change abeam ID, a signal for reporting a TX/RX beam mismatch state to the eNB,a signal for asking the eNB to allocate a UL resource for transmittingBSI or BRI (Beam Refinement Information) feedback on the BF cell, asignal for asking the eNB to transmit a DL RS for beammeasurement/refinement as well as BSI feedback on the BF cell to the eNBvia the non-BF cell (UL data/control channel of a corresponding cell)(for clarity, the abovementioned signals are referred to as“beam-related SR”). And, the UE can report a measurement result for a DLRS for beam measurement/refinement transmitted via the BF cell to theeNB via the non-BF cell. And, the UE can signal information on whetheror not a DL control channel (e.g., a DL/UL grant signal scheduling aDL/UL data channel, etc.) is detected to the eNB via the non-BF cell.For example, the UE can signal information on whether or not a DLcontrol channel is detected via the BF cell during specific duration orinformation on an amount of the DL control channels to the eNB via thenon-BF cell. When the UE operates in the BF cell, the abovementionedoperations are required because a mismatch may occur on a TX/RX beamaccording to a radio channel status and DL/UL signal transmissiontransmitted by the BF cell in the status is not stable.

Meanwhile, the abovementioned proposed operation may not be restrictedto the CA between the non-BF cell and the BF cell. For example, the sameoperation can be applied in a state that the non-BF cell and the BF cellare replaced with a PCell and a SCell or a first cell and a second cell,respectively. More generally, the proposed operation can be applied in astate that the non-BF cell and the BF cell are regarded as a first celland a second cell different from each other or a single cell.

(B) Activation/Deactivation of BF Cell

Unlike a legacy non-BF cell, in case of a BF cell, a (preferred) beam IDmay change during a deactivation period due to a radio channel change,and the like. In consideration of this, a UE can configure the BF cellto perform BSI measurement and (preferred) beam search by receiving aspecific signal (e.g., a synchronization signal or a reference signal)after the BF cell is activated (and report the BSI and the (preferred)beam ID to an eNB). Meanwhile, the UE may not perform a different DL/ULsignal transmission/reception operation in the BF cell until theabovementioned operation is completed.

As a different method, it may be able to configure the UE to performbeam tracking (e.g. BSI measurement, (preferred) beam search) on the BFcell by receiving a specific signal (e.g., a synchronization signal or areference signal) during the deactivation of the BF cell. Hence, the UEcan report (recent) BSI and a (preferred) beam ID to the eNB while theBF cell is activated (via a response message in response to anactivation message). Meanwhile, the eNB can trigger an RS for measuringBSI to be transmitted via an activation message for the BF cell and/orindicate the UE to report a BSI measurement result.

Meanwhile, the non-BF cell normally performs a UL/DL signaltransmission/reception operation during an activation period and doesnot perform a UL/DL signal transmission/reception operation during adeactivation period. For example, the non-BF cell does not receive a DLphysical channel (e.g., PDCCH, PHICH, etc.) during the deactivationperiod and does not perform a CSI/SRS transmission operation.

[4] UL Power Control in Various CA Situations

When CA is performed between cells operating with a different SCS (ordifferent OS duration), if UE maximum power restriction (e.g., the sumof UL power (configured by an eNB) exceeds UE maximum power at the sametiming) occurs, it may consider a method of preferentially reducing a ULchannel/signal power (of a cell) configured by a small SCS (or long OSduration) and/or a method of assigning minimum guaranteed power to a ULchannel/signal (of a cell) configured by a big SCS (or short OSduration). For example, if minimum guaranteed power for a specific ULchannel/signal is defined by G-power and power configured by an eNB isdefined by C-power, final power (i.e., S-power) of the specific ULchannel/signal calculated by a power scaling procedure in the UE maximumpower restriction can be determined by a value equal to or greater thanmin {G-power, C-power} only (i.e., a minimum value of the S-power isrestricted to min {G-power, C-power}). Meanwhile, when CA is performedbetween a non-BF cell and a BF cell, if UE maximum power restrictionoccurs, it may consider a method of preferentially reducing ULchannel/signal power of the non-BF cell and/or a method of assigningG-power to a UL channel/signal of the BF cell.

Meanwhile, when UL channels/signals (e.g., UL data/control channel, ULsounding signal) having the different number of symbols (or havingdifferent time duration) are transmitted at the same time, if UE maximumpower restriction occurs, it may consider a method of preferentiallyreducing power of a UL channel/signal having more symbols (or longertime duration) and/or a method of assigning minimum guaranteed power toa UL channel/signal having less symbols (or shorter time duration).Meanwhile, when UL channels/signals (e.g., UL data/control channel, ULsounding signal) to which a different UL modulation scheme (e.g., OFDMor DFT-based SC-FDM) is applied are transmitted at the same time, it mayconsider a method of preferentially reducing power of a ULchannel/signal to which the OFDM scheme is applied and/or a method ofassigning minimum guaranteed power to a UL channel/signal to which theSC-FDM scheme is applied.

The abovementioned proposed method can be applied in consideration of apower scaling priority (e.g., power is reduced in an order of randomaccess signal > control channel > data channel > sounding signal)between UL channels/signals and a power scaling priority between UCItypes (e.g., power is reduced in an order of A/N>SR>CSI, A/N=SR>CSI, orSR>A/N>CSI). For example, power scaling is performed according to thepriority between UL channels/signals and the priority between UCI typesafter the proposed scheme is preferentially applied. Or, the proposedscheme is applied between channels/signals and UCI types having the samepriority after the power scaling is performed according to the prioritybetween UL channels/signals and the priority between UCI types.

Meanwhile, it may be able to assign a power scaling priority higher thana priority of a different UCI type (e.g. A/N, CSI) to a beam-related SR(irrespective of whether or not CA is configured). For example, if UEmaximum power restriction occurs, it may be able to preferentiallyreduce signal power of a different UCI type compared to a beam-relatedSR signal. Specifically, a power scaling priority (equal to or) lowerthan A/N is assigned to a general data SR requesting a UL datatransmission resource. On the contrary, it may be able to assign a powerscaling priority higher than A/N to a beam-related SR. As a differentexample, while a power scaling priority lower than a random accesssignal is assigned to a general data SR, it may be able to assign apower scaling priority higher than a random access signal to abeam-related SR. Meanwhile, a (contention-based) random access signalresource capable of being selected/transmitted by a UE in an initialaccess or an idle mode (to prevent excessive contention and congestionin a random access situation) and a (contention-based) random accesssignal resource capable of being selected/transmitted by a UE (torequest scheduling) in a connected mode can be configured to bedistinguished from each other in time/frequency/code.

[5] Method of Performing CA Including Non-Standalone SCell

In NR system environment, a SCell configuring CA may operate in a formof standalone or non-standalone. In particular, when CA including anon-standalone SCell is performed, 1) an eNB can aperiodically triggertransmission of a specific (UE-common) signal (e.g., a synchronizationsignal, system information, or a reference signal) in the SCell and 2) aUE may aperiodically request the transmission of the specific signal.When (potential or candidate) timing and a period capable oftransmitting the specific signal is configured in advance, if there is atransmission of a trigger signal of an eNB or a transmission of arequest signal of a UE for the specific signal via random timing, it mayconsider a method of transmitting and receiving the triggered/requestedspecific signal via timing and a period closest from the timing at whichthe trigger/request signal is transmitted (or timing to which a specifictime offset is added). In this case, the trigger signal of the eNB orthe request signal of the UE for the specific signal can be transmittedvia a cell (e.g., PCell) operating in a form of standalone.

Meanwhile, in case of a standalone cell, transmission of a specific(UE-common) signal (e.g., a synchronization signal, specific partialsystem information (except information necessary for performing initialaccess stage/procedure ((e.g. random access signal/resourceconfiguration)), a reference signal, etc.) can be aperiodicallytriggered/requested by an eNB or a UE. In this case, the aforementionedproposed method can be identically applied. More generally, the proposedmethod is not restricted to CA between a standalone cell and anon-standalone cell. The same operation can be applied in a state thatthe standalone cell and the non-standalone cell are replaced with aPCell and a SCell or a first cell and a second cell, respectively. Moregenerally, the proposed method can be applied in a state that thestandalone cell and the non-standalone cell are regarded as a first celland a second cell different from each other or a single cell.

Meanwhile, it may be able to configure either standalone cells (i.e.,SA-cells) or non-standalone cells (i.e., NSA-cells) to belong to asingle DCIG only. In particular, it may be able to configure an SA-celland an NSA-cell not to belong to the same DCIG Or, if an SA-cell and anNSA-cell are configured to belong to a single DCIG without a separateDCIG configuration restriction, it may be able to configure a DL controlchannel (DCI) to be transmitted via an SA-cell only. To this end, it maybe able to configure at least one SA-cell to belong to a DCIG Similarly,it may be able to configure either SA-cells or NSA-cells to belong to asingle UCIG only. In particular, it may be able to configure an SA-celland an NSA-cell not to belong to the same UCIG In this case, if anSA-cell and an NSA-cell are configured to belong to a single UCIGwithout a separate UCIG configuration restriction, it may be able toconfigure a UL control channel (UCI) to be transmitted via an SA-cellonly. To this end, it may be able to configure at least one SA-cell cellto belong to a UCIG Additionally, it may be able to configure eitherSA-cells or NSA-cells to belong to a single TAG only. In particular, itmay be able to configure an SA-cell and an NSA-cell not to belong to thesame TAG In this case, if an SA-cell and an NSA-cell are configured tobelong to a single TAG without a separate TAG configuration restriction,it may be able to configure a random access signal to be transmitted viaan SA-cell only. To this end, it may be able to configure at least oneSA-cell to belong to a TAG

Meanwhile, when a single cell or a carrier is divided into a pluralityof subbands and an SCS or a TTI of a different size is set to each of aplurality of the subbands, although a UE operates on a plurality of thesubbands at the same time or switches between subbands, all of theproposed methods of the present invention can be similarly applied (in amanner of replacing a cell with a subband).

FIG. 20 illustrates a BS and a UE of a wireless communication system,which are applicable to embodiments of the present invention.

Referring to FIG. 20, the wireless communication system includes a BS110 and a UE 120. When the wireless communication system includes arelay, the BS or UE may be replaced by the relay.

The BS 110 includes a processor 112, a memory 114 and a radio frequency(RF) unit 116. The processor 112 may be configured to implement theprocedures and/or methods proposed by the present invention. The memory114 is connected to the processor 112 and stores information related tooperations of the processor 112. The RF unit 116 is connected to theprocessor 112 and transmits and/or receives an RF signal. The UE 120includes a processor 122, a memory 124 and an RF unit 126. The processor122 may be configured to implement the procedures and/or methodsproposed by the present invention. The memory 124 is connected to theprocessor 122 and stores information related to operations of theprocessor 122. The RF unit 126 is connected to the processor 122 andtransmits and/or receives an RF signal.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It will beobvious to those skilled in the art that claims that are not explicitlycited in each other in the appended claims may be presented incombination as an embodiment of the present invention or included as anew claim by a subsequent amendment after the application is filed.

In the embodiments of the present invention, a description is madecentering on a data transmission and reception relationship among a BS,a relay, and an MS. In some cases, a specific operation described asperformed by the BS may be performed by an upper node of the BS. Namely,it is apparent that, in a network comprised of a plurality of networknodes including a BS, various operations performed for communicationwith an MS may be performed by the BS, or network nodes other than theBS. The term ‘BS’ may be replaced with the term ‘fixed station’, ‘NodeB’, ‘enhanced Node B (eNode B or eNB)’, ‘access point’, etc. The term‘UE’ may be replaced with the term ‘Mobile Station (MS)’, ‘MobileSubscriber Station (MSS)’, ‘mobile terminal’, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

The present invention is applicable to UEs, eNBs or other apparatuses ofa wireless mobile communication system.

What is claimed is:
 1. A method of performing communication by a userequipment in a wireless communication, the method comprising:aggregating a first cell having a first TTI (Transmission TimerInterval) length with a second cell having a second TTI length, whereinthe second TTI length corresponds to N (N>1) multiple of the first TTIlength; receiving data scheduling information for the second cell withina first TTI of the first cell; and performing data communication withina second TTI of the second cell corresponding to the first TTI of thefirst cell based on the data scheduling information, wherein the firstTTI of the first cell corresponds to one of the N TTIs of the first cellcorresponding to the second TTI of the second cell.
 2. The method ofclaim 1, wherein the N TTIs of the first cell corresponding to thesecond TTI of the second cell are divided into TTI groups and whereinthe first TTI of the first cell corresponds to a TTI belonging to aspecific TTI group among the TTI groups.
 3. The method of claim 2,wherein a position of a TTI corresponding to the first TTI of the firstcell varies over time in the specific TTI group.
 4. The method of claim1, wherein the first TTI of the first cell corresponds to a TTIoverlapped with a first OFDM symbol in time domain among a plurality ofOFDM (Orthogonal Frequency Division Multiplexing) symbols constructingthe second TTI of the second cell among the N TTIs of the first cellcorresponding to the second TTI of the second cell.
 5. The method ofclaim 1, further comprising: sequentially monitoring the N TTIs of thefirst cell corresponding to the second TTI of the second cell to receivethe data scheduling information for the second cell, wherein if the datascheduling information for the second cell is detected, although thereis a TTI to be monitored, monitoring on the N TTIs of the first cell isterminated.
 6. The method of claim 1, wherein a subcarrier spacingconfigured to the first cell is greater than a subcarrier spacingconfigured to the second cell.
 7. A user equipment in a wirelesscommunication system, the user equipment comprising: an RF (RadioFrequency) module; and a processor, the processor configured toaggregate a first cell having a first TTI (Transmission Timer Interval)length with a second cell having a second TTI length, wherein the secondTTI length corresponds to N (N>1) multiple of the first TTI length, toreceive data scheduling information for the second cell within a firstTTI of the first cell, and to perform data communication within a secondTTI of the second cell corresponding to the first TTI of the first cellbased on the data scheduling information, wherein the first TTI of thefirst cell corresponds to one of the N TTIs of the first cellcorresponding to the second TTI of the second cell.
 8. The userequipment of claim 7, wherein the N TTIs of the first cell correspondingto the second TTI of the second cell are divided into TTI groups andwherein the first TTI of the first cell corresponds to a TTI belongingto a specific TTI group among the TTI groups.
 9. The user equipment ofclaim 8, wherein a position of a TTI corresponding to the first TTI ofthe first cell varies over time in the specific TTI group.
 10. The userequipment of claim 7, wherein the first TTI of the first cellcorresponds to a TTI overlapped with a first OFDM symbol in time domainamong a plurality of OFDM (Orthogonal Frequency Division Multiplexing)symbols constructing the second TTI of the second cell among the N TTIsof the first cell corresponding to the second TTI of the second cell.11. The user equipment of claim 7, wherein the processor is configuredto sequentially monitor the N TTIs of the first cell corresponding tothe second TTI of the second cell to receive the data schedulinginformation for the second cell and wherein if the data schedulinginformation for the second cell is detected, although there is a TTI tobe monitored, monitoring on the N TTIs of the first cell is terminated.12. The user equipment of claim 7, wherein a subcarrier spacingconfigured to the first cell is greater than a subcarrier spacingconfigured to the second cell.